When an aircraft dives towards the ground the aircraft may crash if the pilot, or an autopilot, does not avoid the collision. To increase the safety it is known to calculate a recovery flight path, which evades collision with the ground. For high-performance aircrafts it is also known to calculate or to simulate an altitude or a point of time at which an evasive action must be initiated. Such a calculation system is particularly useful when the diving path is steep or when the aircraft dives inverted. In the latter case the aircraft is first rolled to wings level, after which the aircraft is pitched upwards. Such a recovery flight path is called a zenith recovery flight path and is shown in FIG. 1 marked with the reference letter A. When an aircraft dives steeply and inverted it may in some instances be better to continue the diving path by pitching the aircraft at once. The aircraft then first descends more steeply, turns backwards in a loop-like flight path and ascends in the other direction so that a collision with the ground is avoided. Such a flight path is called a nadir recovery flight path and is also shown in FIG. 1 marked with the reference letter B.
For high performance aircrafts, such as military aircrafts, it is necessary to take both the zenith and the nadir recovery flight paths into account. In this case a number of problems occur. To calculate a recovery flight path demands a lot of computational power, which always is in shortage. To make a calculation for both types of flight paths demands twice as much computational power as when calculating only one flight path. In addition the two different flight paths must be compared with each other in order to choose the best one, which also demands computational power, and, if the comparison is inconclusive, the system may switch back and forth between the two recovery flight paths. The computation is then in danger to give contradictory answers which can be dangerous. Furthermore, the nadir recovery flight path B, may in some instances in itself cause a collision with the ground since the aircraft dives even more steeply in the beginning of the flight path.